Permeable porous composite

ABSTRACT

A porous and permeable composite for treatment of contaminated fluids, said composite including a body of iron particles and 0.01-10% by weight of at least one functional ingredient distributed and locked in the pores and cavities of the iron body. Also, methods of making a permeable porous composite for water treatment. Also, use of a permeable porous composite for reducing the content of contaminants in a fluid, wherein said fluid is allowed to pass through the permeable composite.

FIELD OF THE INVENTION

The present invention concerns a composite containing iron particles andat least one functional ingredient. The particles of the functionalingredients are well distributed in a permeable porous iron body. Thepresent invention also concerns the method of making the composite, andthe use of the composite for purifying fluids. The composite can bemanufactured into powder form, pellet form and various other forms byusing powder metallurgical processes.

BACKGROUND OF THE INVENTION

Toxic inorganic/organic substances in various water sources have to bereduced below regulated levels before the water goes into drinking watersystems or is released into recipients.

Nitrate (NO₃ ⁻) is the most common inorganic contaminant found ingroundwater in the areas where agriculture activities occur heavily.Nitrates usually come from fertilizers, used in farming and gardening inorder to provide the plants and shrubs with nutrients.

Other contaminants which may be generated from such activities arephosphates (PO₄ ³⁻) and traces of pesticides such as atrazine.Accumulation of fertilizers is a problem as they can go through the soiland contaminate ground water systems. Both shallow water wells and deepwater wells can be affected.

Toxic metals such as arsenic (As), chromium (Cr), whereof its oxidationstate +6 (Cr^(VI)) is regarded as most harmful, lead (Pb), mercury (Hg),cadmium (Cd), selenium (Se), etc, other substances as chlorinatedhydrocarbons and other organic substances, sometimes measured as TotalOrganic Carbon (TOC) are generated either from natural origins or fromindustrial or farming activities.

In order to reach acceptable levels of contaminants in drinking water,several processes are currently used.

Reverse osmosis is based on the process of osmosis. This involves theselective movement of water from one side of a membrane to the other. Amajor disadvantage of reverse osmosis is the large amount ofcontaminated wastewater generated, which can be as much as 50 to 90% ofthe incoming water. Over time, clogging of the membrane pores occurs asiron, salts and bacteria accumulate on the membrane surface. This notonly affects the performance of the reverse osmosis system, but can alsocause bacterial contamination of the water. This technique is also veryenergy consuming.

Distillation processes are also used. The nitrate and other mineralsremain concentrated in the boiling tank. The disadvantages of thisprocess include the amount of energy consumed (to boil the water),limited capacity and constant maintenance.

The ion exchange process percolates water through bead-like sphericalresin materials (ion-exchange resins). Ions in the water are exchangedfor other ions fixed to the beads. The two most common ion-exchangemethods are softening and deionization. Ion exchange techniques alsogenerate hazardous brine waste that needs to be deposited. Deionization(DI) systems effectively remove ions, but they do not effectively removemost organics or microorganisms. Microorganisms can attach to theresins, providing a culture media for rapid bacterial growth andsubsequent pyrogen generation. This technique has a low initial capitalinvestment but a high long-term operational cost.

US patent publication No. 2007/0241063A1 describes a process fortreating water contaminated with a volatile organic compound with ironpowder granules containing iron, carbon and oxygen. The carbon additionto the iron powder granules in US2007/0241063A1 is made during theatomization process and are not subjected to any mixing process. This iscommonly known as a “pre-alloy” process in the field of powdermetallurgy.

U.S. Pat. No. 5,534,154 describes a procedure for treating contaminatedwater by passing the water containing contaminant in solution through apermeable body of treatment material comprising particles of anadsorptive material physically mixed with particles of metal. The ironmetal particles mentioned in the patent are iron fillings generally insolid granular form. The procedure requires a negative Eh voltage whichin turn demands oxygen exclusion.

U.S. Pat. No. 6,827,757 describes a magnetite-iron based composite withvery small average particle size of 0.05-10 μm.

EP1273371A2 describes an iron powder adapted to remediate selected mediaby dehalogenating halogenated hydrocarbons in the media comprising ironpowder particles and inorganic compounds. Said inorganic compoundsshould have a very low electric resistivity, preferably selected fromthe group consisting of Ca, Ti, V and Cr. Said inorganic compoundsshould be present on at least a portion of the surface of each particle.

SUMMARY OF THE INVENTION

An object of the invention is to provide permeable porous compositescomprising an iron body suitable for contaminant purification of fluids,especially liquids, such as water. The composites can be applied influid treatments such as drinking water treatment, waste water treatmentsuch as municipal and industrial waste water treatment, and also forsoil remediation. Further the permeable porous composite has functionalingredients in their free form well distributed and locked in the poresof an iron body. The term ‘locked in’ refers to the effect of attachingfunctional ingredient particles to the iron body in such a way that theywill not be removed from the iron body by the fluid during thepurification process. Another object of the invention is to provide themethod of making the iron-based composite.

Yet another object of the invention is to provide a method for purifyingliquids, such as water, from contaminants with no generation ofhazardous waste products.

Yet another preferred object of the invention is to provide a productand method for reducing nitrates in water, especially water to be usedas drinking water.

The present invention relates to a porous and permeable composite fortreatment of contaminated fluids characterized in that said compositecomprises a body of iron particles and 0.01-10% by weight of at leastone functional ingredient distributed and locked in the pores andcavities of the iron body. A body of iron particles is to be interpretedas a body of particles as they are in original state or the ironparticles have been formed into a different shape (an iron body).

A permeable porous composite, comprising 0.01%-10% by weight of at leastone functional ingredient, preferably selected from the group consistingof carbon containing compounds, calcium containing compounds, sodiumcontaining compounds, iron containing compounds, titanium containingcompounds and aluminium containing compounds; preferably said carboncontaining compounds are selected from graphite, activated carbon (AC)and coke; said iron containing compounds are selected from ferric orferrous sulphate, ferric oxides and ferric hydroxides; said titaniumcontaining compounds is titania; and said aluminium containing compoundsare selected from alumina, activated alumina and aluminium silicatessuch as zeolites; said sodium containing compound is soda; said calciumcontaining compounds is lime; preferably said functional ingredient isfrom the group of graphite, activated carbon, coke, activated aluminaand zeolites, most preferably from the group of graphite, activatedcarbon, coke. Optionally may further functional ingredients outside thementioned group be selected, depending on the contaminant to beprocessed. All functional ingredients should be locked in and welldistributed in the permeable porous iron body.

The present invention also relates to methods of making a permeableporous composite e.g. for water treatment. Said composite can bemanufactured into various forms, such as powder, chip, flake, block orpellet, using common powder metallurgical technologies.

A method for manufacturing a porous and permeable composite fortreatment of contaminated fluids, comprising the steps of; mechanicallymixing iron particles representing an iron body with at least onefunctional ingredient, which is present in an amount of 0.01-10% byweight, until the functional ingredient is distributed by mechanicalforces into the iron body and locked; optionally heat treating the ironbody, with or without said at least one functional ingredient, at atemperature between 300 and 1200° C. in an inert or reducing atmosphere;optionally compacting the iron body, with or without said at least onefunctional ingredient, into a compacted body having a green densityequal to or below 7.0 g/cm³; and/or optionally sizing said iron body,with or without said at least one functional ingredient, wherein saidsteps can be carried out in optional order.

The present invention also relates to use of a permeable porouscomposite according to any preceding claims for reducing the content ofcontaminants in a fluid, wherein said fluid is allowed to pass throughthe permeable composite. Said fluid may be a water containing fluid,preferably ground water, river water, industrial waste water, civicwaste water and/or surface water. Said fluid may be used as drinkingwater after purification treatment according to the present invention.Said contaminants may be selected from the group consisting of nitrate,nitrite, heavy metals, such as As, Pb, Hg, Cd, Se, Cr and hexavalent Cr,other toxic inorganic substances and toxic organic compounds; orcombinations thereof; preferably nitrate and/or nitrite.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The permeable and porous composite according to the present inventioncomprises a mixture of porous iron, and 0.01-10%, preferably 0.05-8%,preferably 0.1-5% by weight of at least one functional ingredient whichmight be chosen from coke, graphite, activated carbon, ferric oxides,ferric hydroxides, titania, alumina, activated alumina, zeolites, lime,soda, ferric or ferrous sulphate, preferably from the group of coke,graphite, activated carbon, activated alumina and zeolites. Depending ofthe pore and cavity size of the permeable porous iron, the functionalingredient may have in some embodiments of the invention a particle sizeless than 20 μm, preferably less than 10 μm, in other embodiments theparticle size of the functional ingredients may be less than 10 μmpreferably less than 5 μm. The particle size being above about 0.02 μm.

The use of the wording “permeable” as disclosed herein is to beinterpreted as a composite or a iron powder or body being constructed sothat it is permeated or penetrated, especially by liquids or gases. Theuse of the wording “porous” as disclosed herein is to be interpreted asa composite or a iron powder or body being constructed so that it isadmitting the passage of gas or liquid through pores or interstices.Thus, the permeable and porous composite according to the presentinvention comprises the at least one functional ingredient located inpores and cavities of the composite. The iron part of the composite, theiron body, could be made of iron powder or iron particles whichthemselves are porous. Otherwise, the iron body, the porous andpermeable iron structure, is prepared using compaction and/or heat andoptional sizing of iron powder or particles.

The iron particles or powder are/is mixed with the functional ingredientresulting in a composite according to the invention. Also, the ironpowder can be mixed with the functional ingredient(s) before beingcompacted and/or heat treated, optionally followed by sizing into adesired size. Alternatively, the iron powder can be compacted and/orheat treated, optionally followed by sizing into a desired size, beforebeing mixed with the functional ingredient(s).

All functional ingredients should be locked in and well distributed inthe permeable porous iron body or iron structure. The functionalingredients are in free from, i.e. still in their original state, andthus not altered in any way like alloyed or coated to the iron body.Apart from obtaining a combined technical effect from the adsorptivecapacity of the functional ingredient and the redox ability from theporous iron a synergetic effect is obtained when combining the porousiron with the functional ingredient locked into the pores of the iron.The term functional ingredient should be interpreted as an additivewhich main function is to enhance the purification of fluids, byproviding a synergetic effect with the iron particles. This synergeticeffect is evident by the remarkable high efficiency of the new permeableporous composite for removal of multiple contaminants for examplenitrate and arsenic in combination in water. An additionally advantagewith the method for reducing contaminants in fluids according to thepresent invention is, in contrast to methods such as conventional ionexchange is that no hazardous waste is generated by the method.

In one embodiment porous iron powder particles having a particle sizerange between 10 mm and 10 μm, preferably between 5 mm and 20 μm andmost preferably between 2 mm and 45 μm is preferably used. Finer ironpowder may also be used and can in these cases be turned into coarserporous particles by known methods such as compaction and sizing; heattreatment and sizing; or compaction, heat treatment and sizing. The ironpowders used in these cases may have particle size range between 2 mmand 1 μm, preferably between 1 mm and 1 μm, and preferably 0.5 mm and 1μm. Having too small average particle size increases the oxidation rateof the iron particles to too high levels, meaning a loss of processefficiency. Depending on the application, i.e. type of fluid to betreated and type of contaminants, different iron powders and differentfunctional ingredients could be chosen in order to obtain optimalefficiency. For reducing nitrate content in drinking water, chemicallyreduced iron powder has shown to be one preferred embodiment of thepresent invention.

Preferably, the iron powder has a content of Fe of more than 90% iron,preferably more than 95%. Iron powder particles used may originatedirectly from atomization of molten iron i.e. gas atomization and wateratomization of molten iron, chemical reduction of iron oxides such asCO-reduction or H2-reduction of iron oxides and thereafter being mixedwith the functional ingredients optionally followed by other processessteps, such as compaction, heat treatment, sizing or combinationsthereof.

The iron particles or iron powder used may be iron particles having aparticle size range between 10 mm and 10 μm, preferably between 5 mm and20 μm and most preferably between 2 mm and 45 μm but is not to beinterpreted as limited to these particle sizes. If the iron particlesare going to be subjected to compaction and/or heat smaller particlesizes could be used e.g. between 2 mm and 1 μm, preferably between 1 mmand 1 μm, and preferably 0.5 mm and 1 μm. Further, in another embodimentthe iron particles are preferably porous iron particles, i.e. theparticles are themselves porous.

The functional ingredient is added to the iron body, i.e iron particlesor iron particle structure, in an amount of with 0.01%-10% preferably0.05-8%, preferably 0.1-5% by weight of at least one functionalingredient. The particle size of the functional ingredients may be lessthan less than 20 μm, preferably less than 10 μm, and in some cases alsopreferably less than 5 μm e.g. preferably 0.01-20 μm, preferably 0.01-10μm, preferably 0.02-10 μm, preferably 0.02-5 μm.

Mixing of the iron powder or particles with the at least one functionalingredient is performed by mechanical mixing in such a way that thesmall functional particles are forced into the internal porosity of thepermeable iron particle structure and become locked in the structure.

Compaction of a disclosed material is done at pressures below 1000 MPa,preferably below 600 MPa, e.g. 10-1000 MPa or 20-600 MPa, to achieve acompacted density of about or less than 7.0 g/cm³ to form desiredshapes, such as blocks, granules or pellets. Preferably the compacteddensity is between 2.5-7.0 g/cm³, preferably 4-6 g/cm³ depending of typeof iron powder used. The compaction process forces, if a functionalingredient is present, the free smaller functional ingredient particlesto be locked inside the iron body. An iron powder having irregular shapeand a porous structure can provide high green strength to the permeableporous composite thus allowing lower density promoting higherpermeability.

Embodiments requiring heating treatment to achieve a porous andpermeable composite according to the invention would involvetemperatures below 1200° C., below 1000° C., or below 800° C. dependingon the types iron powder and functional ingredients used in a reducingor inert atmosphere. The heat treatment temperature being above 300° C.,preferably above 400° C. Temperature intervals of interest areespecially 300-1200° C., 400-1200° C., 300-1000° C., 400-1000° C.,300-800° C., 400-800° C., 300-700° C., 400-700° C., 300-600° C.,400-600° C., 300-500° C. and 400-500° C. The heat treatment according tothe present invention induces bonding between iron particles, so-calledthermal bonding. If a functional ingredient is present, the heattreatment temperature should also be chosen so that the functionalingredient is kept in its original state, e.g. not diffusing into theiron structure. Also, the heat treatment process forces the free smallerfunctional ingredient particles to become locked inside the permeableporous iron body.

Sizing of a disclosed iron material into particles before an addition ofthe at least one functional ingredient preferably results in a particlessize range between 10 mm and 10 μm, preferably between 5 mm and 20 μmand most preferably between 2 mm and 45 μm.

The mixing step may be performed in an ordinary mixer, such as a Z-blademixer, cone mixer, ribbon mixer or high speed mixer for a period of timebetween 0.5 min och 8 hours, preferably 1 minute to 5 hours or 30 min to3 hours. Compaction may be performed in any suitable compactionequipment such as a ordinary uniaxial press at a pressure below 1 000MPa or in high velocity compaction machine. Heat treatment may beperformed in a batch oven or a continuous mesh belt furnace at atemperature of 300-1200° C. for a period between 5 minutes and 24 hours,e.g. 30 min to 18 hours, 1-12 h, 2-8 h. Sizing or gently grinding may beperformed in any suitable equipment giving a particle size between 10 mmand 10 μm, preferably between 5 mm and 20 μm and most preferably between2 mm and 45 μm.

(1) In one embodiment of the present invention chemically reduced porousiron particles having a particle size range between 10 mm and 10 μm aremechanically mixed with at least one functional ingredient. The particlesize of the functional ingredients may be less than 10 μm, preferablyless than 5 μm. The mechanical mixing is performed in such a way thatthe small particles are forced into the internal porosity of the porousiron particles, such as sponge-like reduced iron powder, and becomelocked in the structure.

(2) In another embodiment of the present invention, iron powderparticles, having particle size range between 2 mm and 1 μm, preferablybetween 1 mm and 1 μm, and preferably 0.5 mm and 1 μm, are subjected toheat treatment at 300-1200° C., depending on particle size, the typesiron powder and functional ingredients, in a reducing or inertatmosphere. After heat treatment the resulting powder cake is sized intoporous iron powder with desired size. The heat treated and sized powderis then mechanically mixed with 0.01-10% by weight of at least onefunctional ingredient. The particle size of the functional ingredientsmay be less than 10 μm, preferably less than 5 μm. The mechanical mixingis performed in such a way that the small functional particles areforced into the internal porosity of the iron particles, and becomelocked in the structure.

(3) In yet another embodiment iron particles having a particle sizerange between 10 μm and 10 mm are mixed with 0.01-10% by weight of atleast one functional ingredient. The particle size of the functionalingredients being less than 20 μm, preferably less than 10 μm. Saidmixture is to subjected to be compaction at pressures below 1000 MPa,preferably below 600 MPa, to achieve a compacted density between 2.5-7.0g/cm³, preferably 4-6 g/cm³ depending of type iron powder used, intodesired shapes such as blocks, granules or pellets. The compactedcomposite may alternatively be sized into desired size. The compactionprocess forces the free smaller functional particles to be locked insidethe porous iron body. An iron powder having irregular shape and a porousstructure can provide high green strength to the permeable porouscomposite thus allowing lower density promoting higher permeability.

(4) In yet another embodiment iron particles having a particle sizerange above between 10 mm and 10 μm, preferably between 5 mm and 20 μmand most preferably between 2 mm and 45 μm are mixed with 0.01%-10%,preferably 0.1-5% by weight of at least one functional ingredient. Theparticle size of the functional ingredient being less than 20 μm,preferably less than 10 μm. Said mixture is subjected to heat treatmentat 300-1200° C. in a reducing or inert atmosphere. After heat treatmentthe resulting powder cake is sized into desired size. The heat treatmentprocess forces the free smaller particles to be locked inside the porousiron powder.

(5) In yet another embodiment iron particles having a particle sizerange above between 10 mm and 10 μm are mixed with 0.01%-10% by weightof at least one functional ingredient. The particle size of thefunctional ingredient being less than 20 μm, preferably less than 10 μm.Said mixture is subjected to powder compaction at pressures below 1000MPa to achieve a compacted density of less than 7.0 g/cm³ to formdesired shapes, such as blocks, granules or pellets. The compactionprocess forces the free smaller particles to be locked inside the ironbody. Said compact is then subjected to heat treatment at 300-1200° C.,depending on the particle size, types iron powder and functionalingredients used, in a reducing or inert atmosphere. The heat treatmenttemperature should be also chosen so that the functional ingredient iskept in its original state, e.g. not diffusing into the iron structure.The compacted and heat treated composite may alternatively be sized intodesired size.

(6) In an alternative embodiment iron particles having a particle sizerange between 2 mm and 1 μm, preferably between 1 mm and 1 μm, andpreferably 0.5 mm and 1 μm is subjected to compaction at pressures below1000 MPa to achieve a compacted density between than 2.5-7.0 g/cm³, or4-6 g/cm³ depending of type iron powder used, to form desired shapes,such as blocks, granules or pellets. The compacted body being then sizedinto particles having a particles size range between 10 mm and 10 μm.The sized material are mechanically mixed with 0.01%-10% by weight of atleast one functional ingredient. The particle size of the functionalingredient may be less than 10 μm, preferably less than 5 μm. Themechanical mixing is performed in such a way that the small functionalparticles are forced into the internal porosity of the porous ironparticles and become locked in the structure.

(7) In an alternative embodiment iron particles having a particle sizerange between 2 mm and 1 μm, preferably between 1 mm and 1 μm, andpreferably 0.5 mm and 1 μm is subjected to compaction at pressures below1000 MPa to achieve a compacted density between than 2.5-7.0 g/cm³, or4-6 g/cm³ depending of type iron powder used, to form desired shapes,such as blocks, granules or pellets. The compacted body is subjected toheat treatment at 300-1200° C., depending on the particle size, typesiron powder and functional ingredients used, in a reducing or inertatmosphere. The heat treated material being then sized into particleshaving a particles size range between 10 mm and 10 μm, preferablybetween 5 mm and 20 μm, and most preferably between 2 mm and 45 μm. Thesized material are mechanically mixed with 0.01%-10% by weight of atleast one functional ingredient. The particle size of the functionalingredient may be less than 10 μm, preferably be less than 5 μm. Themechanical mixing is performed in such a way that the small functionalparticles are forced into the internal porosity of the porous ironparticles and become locked in the structure.

In yet another embodiment a method for producing a porous and permeablecomposite involves a H2-reduced iron powder (porous particles) having aparticle size range between 45 μm and 850 μm in size, and having aFe-content of at least 90% by weight of the iron powder which ismechanically mixed with a functional ingredient chosen from graphiteand/or activated carbon, wherein the functional ingredient is lockedinto the pores of the porous iron particles. The composite comprises abody of H2-reduced iron powder of porous particles having a particlesize range between 45 μm and 850 μm in size and having a Fe-content ofat least 90% by weight of the iron powder, and the functional ingredientis chosen from graphite and/or activated carbon.

In another embodiment of the invention a method for reducing the contentof contaminants in fluids is disclosed comprising the steps of obtaininga permeable porous composite as described above and allowing thecontaminated fluid to pass through the permeable composite thus reducingthe content of the contaminants.

The permeable porous composite could be placed inside a containerconnected to the supply system of the fluid to be treated. Suchcontainers could be placed serial or parallel and connected toadditional containers containing other known substances for reducing thecontent of harmful substances in the fluid. The composite according tothe invention preferably has a specific surface area above 0.2,preferably above 0.5 and most preferably above 1 m²/g as measured by BET(Brunauer, Emmett and Teller, 1938).

The permeable porous composite according to the present invention shouldhave a permeability, expressed as porosity ranging from 11 to 68%,preferably 23-50%, regardless of embodiment.

In one embodiment of the present invention the permeable porouscomposite consists of a mixture of porous iron, and 0.01%-10%,preferably 0.1-5% by weight of at least one functional ingredient.

One embodiment of the invention is to apply the composite to drinkingwater treatment, waste water (municipal and industrial) treatment andsoil remediation. The permeable porous composite according to theinvention is designed for optimal treatment of nitrates and nitrites andtoxic inorganic and organic contaminants.

No direct hazardous waste products are generated when using thepermeable porous composite according to the invention for watertreatment.

The generated by product, i.e. the used porous composite, can be used inother industries, for instance as raw material for the steel industry.The composite according to the invention demonstrates greater and moreconsistent performance in removal of nitrate and other contaminantsduring water treatment and results in no direct hazardous waste.

DRAWINGS

FIG. 1 shows a schematic drawing of permeable porous compositesaccording to the invention and different shapes, which the compositecould be made into.

FIG. 2 shows a schematic drawing of a column used for evaluating theperformance of the permeable porous composite according to theinvention.

FIG. 3 shows a schematic drawing of an apparatus used for evaluatingpermeability of the permeable porous composite according to theinvention. Using minimal air pressure to assist water to overcome thesurface tension of water on the composite in order to determine the max.(min.) permeable density (porosity). The composite was compacted intodifferent density (porosity). Measurement of the amount of water passedthrough the composite by time under pressure or no pressure.

FIGS. 4A-B: Examples of production methods according to the invention

FIG. 5: Picture of porous iron particle

FIG. 6: Picture of solid iron particle

FIG. 7: Picture showing functional ingredients (here activated carbon(AC) particles) in free form locked into the pores of porous ironparticles through mechanically mixing process. The porous iron particlestructure have a lighter colour than the encased AC particles.

EXAMPLES

The following materials were used as functional materials;

TABLE 1 Main Average Specific constituent particle size surface areaName % by weight D50, μm (BET) m²/g Activated carbon, AC 95.4% C 3.8 680Graphite A 99.4% C 2.71 250 Graphite B 99.0% C 5.5 10 Ferric oxide 99.1%Fe₂O₃ 0.75 5

Used Functional Ingredients Example 1

A sample of natural occurring water, ground water from Martinsberg, Pa.,USA, was used. Chemical analysis is shown in table 2. The test wasperformed by pumping the water into a column having a test material, asshown in FIG. 3. The empty bed contact time, EBCT, was 25 minutes. Theeffluent water was analyzed with regards to contaminants after certaintime intervals. The content of contaminants at 0 hours is equal to thecontent in the non treated water (influent).

TABLE 2 Nitrate (as N) [mg/l] 22.7 pH 7.33 Alkalinity [mg/l] 220 Acidity[mg/l] <1.0 Total hardness [mg/l] 531 Conductivity [mS/cm] 2680

Different materials were tested as permeable materials referring totheir ability to reduce nitrate concentration in the solution. Thefollowing materials were tested;

Material 1; A commercial available activated carbon granular, AC,0.6×2.4 mm size having a specific surface area of 600 m²/g as measuredby BET method.

Material 2; A commercial available solid non porous atomized ironpowder, having a particle size less than 200 μm, having a carbon contentof less than 0.1% by weight dissolved in the iron matrix, and a specificsurface area of less than 0.1 m²/g as measured according to BET.

Material 3; A commercial available solid non porous iron aggregatehaving a carbon content of 3% by weight dissolved in the iron matrix, aspecific surface area of 1.2 m²/g as measured according to BET and asize of 0.3×5 mm.

Material 4; A permeable porous composite according to the presentinvention having a specific surface area of 2.7 m²/g as measuredaccording to BET. The composite being produced by mixing graphite A witha porous hydrogen reduced iron powder having a particle size between10-850 μm, mean particle size of about 250 μm for a period of 30 minuntil the graphite was forced into the pores of the iron powder. Theamount of graphite A in said composite was 1% by weight of thecomposite.

Material 5: A permeable porous composite according to the presentinvention having a specific surface area of 6.7 m²/g as measuredaccording to BET. The composite being produced by activated alumina witha porous hydrogen reduced iron powder having a particle size between10-850 μm, mean particle size of about 250 μm for a period of 30 minuntil the alumina was forced into the pores of the iron powder. Theamount of activated alumina in said composite was 4% by weight of thecomposite.

Material 6: A permeable porous composite according to the presentinvention having a specific surface area of 2.0 m²/g as measuredaccording to BET. The composite being produced by zeolite with a poroushydrogen reduced iron powder having a particle size between 10-850 μm,mean particle size of about 250 μm for a period of 30 min until thezeolite was forced into the pores of the iron powder. The amount ofzeolite in said composite was 4% by weight of the composite.

The test was continuously conducted during a period of 72 hours for eachmaterial. The following table shows the concentration of nitrate ions ineffluent for each material. The concentration of nitrate was measured byan ion selective electrode and expressed as nitrogen content in mg/l.

TABLE 3 Material 4 - Material 5 - Material 6 - permeable porouspermeable porous permeable porous Material 1 - Material 2 - Material 3 -composite - according composite - according composite - accordingcomparative comparative comparative to the invention to the invention tothe invention example example example (graphite A) (activated alumina)(Zeolite) % % % % % % Hours mg/l reduction mg/l reduction mg/l reductionmg/l reduction mg/l reduction mg/l reduction 0 22.4 0 22.4 0 22.4 0 22.40 22.6 0 22.6 0 3 12.3 45.1 21.0 6.3 22.8 0 3.6 83.9 16.8 25.7 21.3 5.86 15.6 30.4 22.5 0 22.4 0 1.9 91.5 13.1 42.0 19.7 12.8 9 18.4 17.9 22.90 22.0 1.8 1.2 94.6 12.4 45.1 12.3 45.6 12 20.2 4.6 22.6 0 22.1 1.3 0.996.0 3.6 84.1 7.6 66.5 24 21.3 4.9 21.7 3.1 21.8 2.7 1.2 94.6 2.6 88.36.5 71.3 28 22.1 1.3 22.4 0 20.4 8.9 0.9 96.0 2.2 90.1 5.0 77.8 32 21.54.1 21.4 4.5 20.0 10.7 0.7 96.9 1.8 91.9 2.9 87.2 48 22.4 0 22.3 0.419.2 14.3 0.9 96.0 2.0 91.3 2.2 90.1 52 22.4 0 21.6 3.6 16.7 25.4 1.195.1 1.7 92.5 2.0 91.3 56 22.4 0 21.9 2.2 16.3 27.2 1.9 91.5 1.7 92.51.9 91.8 72 22.4 0 22.0 1.8 13.0 41.9 1.8 92.0 1.8 91.9 1.8 91.9

As can be seen from table 3 above the permeable porous compositesaccording to the invention are able to reduce the nitrate content duringthe whole test period and above 90% from between 3 to 48 hours ofrunning, depending on the functional ingredient used. Material 1 reducesthe nitrate concentration with about 18-45% up to 9 hours. Material 2shows hardly any reducing effect and material 3 reduces the nitratecontent less than 50 during the test period and only start to work aftera substantial time period.

Example 2

Various permeable porous composites according to the invention, weretested according to the method described in example 1, with regards tothere nitrate reducing ability. The water to be used was taken from thesame source. The permeable porous composites were prepared by mixingdifferent functional ingredients with a porous iron powder obtained byhydrogen reduction of iron oxides and having a particle size between10-850 μm, mean particle size of about 250 μm for a period of 30 minutesuntil the functional ingredient was well distributed and locked into thepores of the permeable porous iron.

In composite 1 1% by weight of AC was used as functional ingredient. Thespecific surface area of composite 1 was 5.7 m²/g as measured by BET.

In composite 2 2% by weight of AC was used as functional ingredient. Thespecific surface area of composite 2 was 12.8 m²/g as measured by BET.

In composite 3 1% by weight of graphite A was used as functionalingredient. The specific surface area of composite 3 was 2.7 m²/g asmeasured by BET.

In composite 4 2% by weight of graphite B and 3% by weight of ferricoxide, Fe₂O₃ were used as functional ingredients. The specific surfacearea of composite 1 was 0.6 m²/g as measured by BET.

The concentration of nitrate was measured by an ion selective electrodeand expressed as nitrogen content in mg/l.

TABLE 4 Composite 1 - Composite 2 - Composite 3 - Composite 4 -according to according to according to according to the invention theinvention the invention the invention N % N % N % N % Hours mg/lreduction mg/l reduction mg/l reduction mg/l reduction 0 22.4 0 22.4 022.4 0 22.7 0 3 13.1 41.5 12.0 46.4 13.6 39.3 21.4 5.7 6 11.8 47.3 9.856.3 1.9 91.5 20.4 10.1 9 7.8 65.2 5.7 74.6 1.2 94.6 19.6 13.7 12 1.792.4 1.3 94.2 0.9 96.0 17.6 22.5 24 1.6 92.9 1.0 95.5 1.2 94.6 9.6 57.728 2.2 90.2 1.5 93.3 0.9 96.0 7.3 67.8 32 2.2 90.2 1.2 94.6 0.7 96.6 6.571.4 48 2.5 88.8 1.0 95.5 0.9 96.0 4.1 81.9 52 2.1 90.6 0.9 96.0 1.195.1 4.1 81.9 56 2.2 90.2 1.7 92.4 1.9 91.5 6.3 72.2 72 1.3 94.2 1.095.5 1.8 92.0 9.1 59.9

As can be seen from table 4 the permeable porous composites 1-3 has acapacity of removal of nitrate with more than 90% after 9-12 hours.Composite 4 reduces the nitrate content to a level of about 70% after 32hours and up to 56 hours of testing.

Example 3

This example shows the ability for a permeable porous compositeaccording to the invention to reduce multiple contaminants in groundwater. The test was performed according to example 1 with the exceptionthat Arsenic, As, phosphate, PO₄ ³⁻, and hexavalant chromium, Cr^(VI),was added, spiked, to the water prior to testing.

The permeable material was the permeable porous composite no 2 used inexample 2.

The concentration of nitrate was measured by an ion selective electrodeand expressed as nitrogen content in mg/l. The concentration ofphosphate and hexavalent Cr was measured by a colometric method and theconcentration of arsenic by atomic absorption analyzer, AAS. Theconcentration of phosphate was expressed as P mg/l. Also concentrationsof As and Cr is expressed in mg/l.

TABLE 5 Nitrate As mg/l PO₄ ³⁻ Cr^(VI) (N) % % (P) % % Hours mg/lreduction mg/l reduction mg/l reduction mg/l reduction 0 23.1 0 1.260 00.285 0 0.273 0 3 5.01 78.3 0.007 99.4 0.064 77.5 0.031 88.6 6 2.30 90.00.007 99.4 0.053 81.4 0.021 92.3 9 1.44 93.8 0.002 99.8 0.053 81.4 0.02790.1 12 1.46 93.7 0.003 99.8 0.048 83.2 0.023 91.6 24 0.49 97.9 0.00699.5 0.058 89.6 0.013 95.2 28 0.61 97.4 0.009 99.3 0.061 78.6 0.012 95.632 0.80 96.5 0.008 99.4 0.059 79.3 0.011 96.0 48 1.00 95.7 0.007 99.40.073 74.4 0.014 94.9

As can be seen from table 5 the permeable porous composite according tothe invention has the capacity of removal multiple combinations ofcontaminants.

Example 4

This example shows the ability for a permeable porous compositeaccording to the invention, composite 2 in example 2, to reduce multiplecontaminants in ground water compared to material 3 in example 1.

The test was performed according to example 1 with the exception thatArsenic, As was added, spiked, to the water prior to testing.

The concentration of nitrate was measured by an ion selective electrodeand expressed as nitrogen content in mg/l and the concentration ofarsenic was measured by AAS.

TABLE 6 Non porous iron powder + 3% graphite - Composite 2 - comparativeexample according to the invention Nitrate % As % Nitrate % As % Hours(N) mg/l reduction mg/l reduction (N) mg/l reduction mg/l reduction 022.5 0 5.300 0 23.0 0 5.400 0 3 21.1 6.2 0.022 99.6 3.9 83.0 0.014 99.76 20.8 7.6 0.013 99.8 3.0 87.0 0.007 99.9 9 21.1 6.2 0.020 99.6 4.5 80.40.083 98.5 12 22.5 0 0.033 99.4 3.6 84.3 0.024 99.6 24 18.1 19.6 0.45891.4 3.0 87.0 0.019 99.6 28 22.0 2.2 0.460 91.3 2.7 88.3 0.011 99.8

As is evident from table 6 the permeable porous composite according tothe invention has in the long run a higher capacity of removal ofarsenic as compared to the comparative example. After 24 hours theability for the comparative material to reduce As is going down whereassuch tendency is not noticed for the composite according to theinvention. The capacity for removal of nitrate is about 80-90% for theinventive material whereas the non porous iron powder having a carboncontent of 3% by weight dissolved in the iron matrix removes nitrate toa limited extent.

Example 5

This example shows how to determine the degree of locking for apermeable porous composite according to the invention.

A porous iron powder was mixed with different functional ingredients, 2%by weight of AC, 1% by weight of graphite A and 2% by weight of graphiteB, respectively, for 20 minutes. Standard sieve analysis were performedon the permeable porous composite and content of carbon was measured inthe different fractions. When the finer functional ingredient is welldistributed and locked into the pores of the porous iron the relativecontent of functional ingredient in the different fractions shall be asclose as possible to the percentage of total material in the fractions.By dividing the content of functional material in a sieve interval withthe total content of functional ingredient, a measure of degree ofdistribution and locking is obtained. In order to achieve a sufficientdistribution and locking of the functional ingredient this measure,relative distribution shall be between 1.50 and 0.50 for intervalscontaining more than 5% by weight of the permeable porous composite.Furthermore, the amount of functional material in the finer fraction,less than 0.075 mm, shall not exceed 30%, preferably not exceed 20% ofthe total amount of functional material.

The porous iron powder used had a Fe content of minimum 97% by weight, acarbon content below 0.1% by weight, an apparent density of 1.3 g/cm³.46.8% by weight was above 0.250 mm, 30.9% by weight above 0.150 mm,13.8% by weight above 0.075 mm and the rest, 8.5% by weight below 0.075mm.

The following table 7 shows the sieve analysis of the differentpermeable porous composite and also the content of carbon in thedifferent sieve fractions.

TABLE 7 Added 2% AC Added 1% graphite A Added 1% graphite B % byDistrib. Relative % by Distrib. Relative % by Distrib. Relative weight %C by of C in distrib. weight % C by of C in distrib. weight % C by of Cin distrib. of comp weight fractions % of C of comp weight fractions %of C of comp weight fractions % of C Total 100 1.91 100.0 1 100 0.98 1001 100 1.99 100.0 1 +0.250 mm 48.6 1.59 40.5 0.83 47.6 0.88 42.7 0.8947.3 1.55 36.9 0.78 +0.150 mm 28.5 2.06 30.7 1.08 27.7 0.96 27.2 0.9829.4 2.23 32.9 1.12 +0.075 mm 14.2 2.36 17.5 1.23 14.2 1.15 16.8 1.1814.9 2.54 19.0 1.28 −0.075 mm 8.7 2.48 11.3 1.30 10.5 1.24 13.3 1.27 8.42.65 11.2 1.33

Example 6 Preparation of the Permeable Porous Composite

This example shows how various types of iron powders can be used forproduction of the permeable porous composite, depending on the method ofpreparation. Iron powders used and method of production shall be chosenso that the permeable porous composite will have less than 20% by weightbelow 75 μm, preferably less than 10% by weight below 75 μm as finerporous iron particles may easily be transported away by the flow ofwater. As functional ingredient 2% of AC was used.

Different types of permeable porous composites were prepared by;

(1) compacting an iron powder into TRS (Traverse Rupture Strength) barsfollowed by sizing, gently grinding into desired size, thereafter mixedwith the functional ingredient,—CSM

(2) compacting an iron powder into TRS bars followed by heat treatmentin an atmosphere of nitrogen followed by sizing, grinding into desiredsize, thereafter mixed with the functional ingredient,—CHSM

(3) mixing the functional ingredient with an iron powder compacting themixture into TRS bars followed by sizing, gently grinding into desiredsize,—MCS

(4) mixing the functional ingredient with an iron powder, compacting themixture into TRS bars followed by heat treatment in an atmosphere ofnitrogen followed by sizing, grinding into desired size,—MCHS

After compaction, green density, porosity and green strength weremeasured. Green strength were also measured after heat treatment.Thereafter the samples were sized into desired size, particle sizedistribution and apparent density were measured on the obtained sizedpowder.

Green density (GD) was measured by dividing the weight of the samplewith the calculated volume.

Green strength (GS), expresses the strength of the porous structure ofthe composite made, was measured according to ASTM B 312-ISO 3995

Porosity was measured based on green density measurements and thespecific density (the density without the porosity) of the material.

Apparent density (AD) was measured using a Hall Flow meter. Specificsurface area (SSA) was measured according to the BET method.

TABLE 8 Preparation of different types of composites and theirefficiency in nitrate reduction Process step Production method 1- CSM 3-MCS 2- CHSM 4- MCHS 2- CHSM 4- MCHS 2- CHSM 4- MCHS Raw iron Iron powderPorous Porous Porous Porous Porous Porous Non porous Non porous material% Fe min 97 min 97 min 97 min 97 min 98 min 98 min 99 min 99 % C max 0.1max 0.1 max 0.1 max 0.1 max 0.1 max 0.1 max 0.1 max 0.1 AD g/cm³ 1.3 1.31.8 1.8 2.4 2.4 3 3 +0.850 mm % wt 0 0 0 0 0 0 0 0 +0.250 mm % wt 46.846.8 0 0 0 0 0 0 +0.150 mm % wt 30.9 30.9 4.9 4.9 1.3 1.3 7.6 7.6 +0.075mm % wt 13.8 13.8 50.2 50.2 45.3 45.3 37.2 37.2 −0.075 mm % wt 8.5 8.544.9 44.9 53.4 53.4 55.2 55.2 SSA m²/g 0.23 0.23 0.2 0.2 0.12 0.12 0.050.05 Mixing process % AC 0 2 0 2 0 2 0 2 Time min 0 20 0 20 0 20 0 20Compaction - Compaction 25000/172 25000/172 30000/206 30000/20630000/206 30000/206 30000/206 30000/206 process & Pressure psi/MPamaterial GD g/cm³ 4.68 4.42 4.96 4.86 5.42 5.35 5.76 5.70 Porosity %40.5 43.8 37.0 38.2 31.1 32.0 26.8 27.6 GS psi/N/mm² 4300/30.1 3810/26.71500/10.5 1100/7.7 1600/11.2 580/4.1 900/6.3 580/4.1 Heat treatment -Temprature ° C. 21 21 538 900 538 900 538 900 process & GS after heat4300/30 3810/26 3960/27.7 4660/32.6 3120/21.8 990/6.9 2890/20.2 930/6.5material treatment psi/N/mm² Sizing process Grinding yes yes yes yes yesyes yes yes Mixing process % AC 2 0 2 0 2 0 2 0 Time min 20 0 20 0 20 020 0 Final product - composite porous porous porous porous porous porousporous porous Sized material % C 2 2 2 2 2 2 2 2 AD g/cm3 1.29 1.37 1.561.48 1.98 1.88 2.78 2.88 +0.250 mm % wt 72 68 73.4 91.1 51.9 63.7 66.256 +0.150 mm % wt 14.1 17.2 3.3 1.9 5.4 8.1 6 10.2 +0.075 mm % wt 12.410.3 15.8 5 29.9 22.6 18.6 23.7 −0.075 mm % wt 1.5 4.5 7.5 2 12.3 5.69.2 10.1 SSA m²/g 12.8 12.8 12.8 12.8 12.8 12.8 12.8 12.8 EfficiencyHours Nitrate (N) mg/l tests  0 22.4 22.4 22.4 22.4 22.4 22.4 22.4 22.4(Nitrate  6 9.6 10.1 12.2 10.5 9.8 11.0 13.5 12.7 reduction) 12 1.7 2.31.5 1.6 2.0 2.1 2.5 2.4 24 1.2 1.0 1.1 1.2 0.9 1.5 1.4 1.6

Table 8 shows that permeable porous composites according to the presentinvention may be produced according to various methods.

For example non porous iron powder can be turned into a permeable porouscomposite having a porosity above 25%, giving sufficient permeability tothe contaminated fluid or liquid. For example non porous iron powder canalso be turned into a porous iron powder or structure.

Finer iron powder can also be used be for producing the permeable porouscomposite with a particle size distribution substantially less than 20%by weight being less than 75 μm. If more than 20% by weight of thepermeable porous composite is less than 75 μm the composite will be lesseffective as the finer fraction tends to be carried away by the liquid.

In order not to disintegrate after processing it is believed that thegreen strength of the compacted material should exceed 500 psi, acriterion which is fulfilled by all examples of example 6.

Example 7

This example shows how the minimum required porosity for the permeableporous composite was measured. Three different iron powders, suitable tobe used for producing the permeable porous composite, and two differentpermeable porous composites according to the invention was tested. Thetest equipment as according to FIG. 3.

The iron powders and the composites were compacted into different greendensities. The permeable porous composites were manufactured accordingto embodiment (3) disclosed earlier.

The materials to be tested were placed in the column and water waspassed. The amount of water penetrating through the test material wasmeasured as ml water after 5 minutes.

The following table 9 shows that the porosity of the permeable porouscomposite has to be more than about 11%. This is evident by test 1 and2. At a porosity of 9.7% no water passes through the composite at anyapplied pressure (test 2). At a porosity of 12.8% water passes throughthe composite at a minimal pressure of 5 psi (0.03 MPa), thus theporosity needed has to be above about 11%.

TABLE 9 Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Iron powder Non porousNon porous Porous Porous Porous Porous % Fe min 99 min 99 min 98 min 97min 97 min 97 % C max 0.1 max 0.1 max 0.1 max 0.1 max 0.1 max 0.1 ADg/cm³ 3 3 2.4 1.3 1.3 1.3 +0.850 mm % wt 0 0 0 0 0 0 +0.250 mm % wt 0 00 46.8 46.8 46.8 +0.150 mm % wt 7.6 7.6 1.3 30.9 30.9 30.9 +0.075 mm %wt 37.2 37.2 45.3 13.8 13.8 13.8 −0.075 mm % wt 55.2 55.2 53.4 8.5 8.58.5 SSA m²/g 0.05 0.05 0.12 0.23 0.23 0.23 mixing no no no no 1% AC 1%graphite A Compacted density, g/cm³ 6.86 7.11 5.96 4.77 4.94 5.00material porosity, % 12.8 9.7 24.3 39.4 37.2 36.5 Permeability time, min5.0 5.0 5.0 5.0 5.0 5.0 test air pressure, ml water ml water ml water mlwater ml water ml water psi/MPa after 5 after 5 after 5 after 5 after 5after 5 minutes minutes minutes minutes minutes minutes  0/0 0 0 0 0 0 0 5/0.034 1 0 3 2 2 2 10/0.069 2 0 5 4 4 4 20/0.138 3 0 11 9 6 7

The invention claimed is:
 1. A porous and permeable composite fortreatment of contaminated fluids wherein said composite comprises a bodyof iron particles and 0.01-10% by weight of at least one functionalingredient, selected from the group consisting of graphite, activatedcarbon and coke, in free form, distributed and locked in the pores andcavities of the iron body, wherein the iron particles have a particlesize range between 20 μm and 5 mm and wherein less than 20% by weight ofthe iron particles have a size less than 75 μm.
 2. A composite accordingto claim 1, wherein the at least one functional ingredient has aparticle size below 20 μm.
 3. A composite according claim 1, wherein theiron particles have a content of Fe of more than 90% iron.
 4. Acomposite according to claim 1, wherein said composite has a specificsurface area above 0.2 m²/g as measured by BET.
 5. A composite accordingto claim 1, wherein the total amount of the at least one functionalingredient is between 0.05-8% by weight.
 6. A composite according toclaim 1, wherein the iron particles are porous.
 7. A composite accordingto claim 1, wherein said composite comprises a body of H2-reduced ironpowder of porous particles having a particle size range between 45 μmand 850 μm in size and having a Fe-content of at least 90% by weight ofthe iron powder, and the functional ingredient is chosen from graphiteand/or activated carbon.
 8. A method of reducing the content ofcontaminants in a fluid, the method comprising passing said fluidthrough the permeable composite according to claim
 1. 9. Methodaccording to claim 8, wherein said fluid is a water containing fluid.10. Method according to claim 8, wherein the content of contaminants isselected from the group consisting of nitrate, nitrite, heavy metals,other toxic inorganic substances and toxic organic compounds; orcombinations thereof.
 11. Method according to claim 8, wherein saidfluid is to be used as drinking water.
 12. A composite according toclaim 1, wherein the at least one functional ingredient has a particlesize 0.02-10 μm.
 13. A composite according claim 1, wherein the ironparticles have a content of Fe of more than 95% iron.
 14. A compositeaccording claim 1, wherein iron powder is manufactured from chemicalreduction of iron oxides or atomization of molten iron.
 15. A compositeaccording claim 1, wherein the composite has a porosity more than about11%.